The present invention generally relates to fabrication of semiconductor devices and more particularly to a vapor-phase processing method and apparatus for use in fabrication process of semiconductor devices.
A CVD process is a typical vapor-phase process used in fabrication process of semiconductor devices for depositing various layers on a substrate. Further, a plasma process such as a dry etching process is another typical example of the vapor-phase process used in the fabrication process of semiconductor devices.
In such a vapor-phase process of a substrate, it is necessary to control the process condition such that formation of particles is eliminated during the vapor-phase process. This requirement of eliminating the particle formation is becoming a particularly acute problem in the case of fabricating advanced, leading-edge semiconductor devices having extremely fine patterns.
Conventionally, control of a vapor-phase process condition has been achieved by detecting the particles that remain on the substrate by examining the substrate surface by way of optical means after the process has been conducted. However, such an optical examination of the substrate surface cannot detect particles having a diameter less than 0.3 xcexcm, while it is thought that the particles of the diameter less than 0.3 xcexcm may cause the problem of rough surface in the processed surface. Further, in view of the fact that the process is not a real-time process, there has been a difficulty in grasping the situation of particle formation in the conventional substrate processing method and apparatus.
In view of the situations noted above, there has been a proposal in the Japanese Laid-Open Patent Application No.11-44654 with regard to a substrate processing apparatus that enables a real-time detection of particle formation.
FIG. 1 shows the construction of a conventional substrate processing apparatus 10 disclosed in the foregoing Japanese Laid-Open Patent Application No.11-44654.
Referring to FIG. 1, the substrate processing apparatus 10 includes a reaction chamber 17 accommodating therein a semiconductor substrate 1 for processing, and a laser beam source 11 that produces a laser beam is provided such that laser beam is injected into the reaction chamber 17. Further, an optical detector 12 is provided for detecting a scattering of the laser beam caused by particles 2 that are formed in the reaction chamber 17 during a vapor-phase processing conducted therein.
More specifically, the reaction chamber 17 has a first optical window 17a for introducing the laser beam into the reaction chamber 17 from the laser beam source 11 and a second optical window 17c is provided such that the laser beam exits through the second optical window 17b after traveling through the reaction chamber 17. Further, the reaction chamber 17 has a third optical window 17b that allows the scattered laser beam to exit from the reaction chamber 17 after being scattered by the particles 2.
Adjacent to the optical window 17a, there is provided a collimating optical system 13 in alignment with the laser beam source 11, and the laser beam of the laser beam source 11 is injected into the optical window 17a via the foregoing optical system 13. The optical detector 12, in turn, is provided adjacent to the optical window 17b and detects the scattered laser beam that has exited from the reaction chamber 17 through the optical window 17b. Further, a beam damper 18 is disposed adjacent to the optical window 17c at the outer side of the reaction chamber 17 so as to absorb the optical beam that has exited the reaction chamber 17 through the optical window 17b. 
In the processing apparatus 10 of FIG. 1, it becomes possible to detect the formation of the particles 2 in the reaction chamber 17 real time, in other words, during the process of depositing a film, by monitoring the scattering of the laser beam by means of the optical detector 12. The film thus formed may be a metal film such as a W film. By setting the optical path of the laser beam such that the laser beam passes a limited region above the substrate 1 in which the probability of particle formation is maximum, it becomes possible to minimize the particle formation in the reaction chamber 17 during the process applied to the substrate 1.
While the prior art processing apparatus 10 of FIG. 1 is thus capable of detecting the formation of particles in real time, there is a drawback in that the apparatus 10 requires a bulky laser beam source 11 and cooperating optical system 13. Further, the processing apparatus 10 requires the optical detector 12. Thus, there arises a problem, particularly when the processing apparatus 10 of FIG. 1 is used to construct a single-wafer processing system or cluster-type wafer processing system together with other various substrate processing apparatuses, in that the space necessary for accommodating the substrate processing apparatus 10 may not be available. Further, the laser beam source 11, typically formed of a YAG laser for producing the laser beam with several watts of output power, or the optical detector 12 typically formed of a high-sensitivity CCD camera for high-sensitivity detection of laser beam scattering, is extremely expensive and increases the fabrication cost of the semiconductor device.
Thus, there has been a difficulty to use the processing apparatus 10 of FIG. 1 for mass production of semiconductor devices.
Accordingly, it is a general object of the present invention to provide a novel and useful processing method of substrate wherein the foregoing problems are eliminated.
Another and more specific object of the present invention is to provide a processing method of a substrate with minimized particle formation.
Another object of the present invention is to provide a method for processing a substrate, comprising the steps of:
(a) determining an allowable margin of processing condition in which a substrate is processed without forming particles;
(b) selecting a processing condition such that said processing condition falls in said allowable margin; and
(c) carrying out a processing of a substrate at said selected processing condition, said step (a) for determining said allowable margin comprising the steps of:
(a1) setting a process condition;
(a2) introducing an optical beam to an atmosphere in which said substrate is processed;
(a3) carrying out a processing of said substrate in said atmosphere;
(a4) detecting a scattering of said optical beam; and
(a5) changing said processing condition.
According to the present invention, it is possible to fabricate a semiconductor device efficiently by first determining the allowable margin of process condition in the step (a) and then setting the process condition within the allowable process margin in the steps (b) and (c). By using different processing apparatuses for the step (a) and for the steps (b) and (c), it is possible to eliminate the optical beam source or the optical detector for detecting the scattered optical beam in the processing apparatus used in the steps (b) and (c) for mass-producing semiconductor devices. According to such a construction, the processing apparatus used for the steps (b) and (c) has a simplified construction and a compact size, and thus, can be used to construct a single-wafer processing system together with other various processing apparatuses. According to the present invention, it becomes possible to control the formation of ultrafine particles having a particle diameter of several-ten nanometers or less, of which control has been difficult when conventional particle monitor devices are used.
Other objects and further features of the present invention will become apparent from the following detailed description when read in conjunction with the attached drawings.